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04 December 1997 AGE-NC Protect No 95-0128 Page 2 of 5 ' 22 GROUND WATER SAMPLE COLLECTION Following purging and recovery of the ground water monitoring wells, a water sample was collected from each purged well using new, clean, disposable plastic bailers Immediately upon retrieval, ground water samples were transferred into chilled 40-m1 EPA approved VOA vials containing 0 5 ml 18% hydrochloric acid and into I-liter amber bottles Additionally, an amber liter and quart of water was collected from well MW-4 and vapor well VW-I Samples were placed in a chilled container, under ice and transported under chain-of-custody to Me Campbell Analytical, Inc , (MAI) in Pacheco, California Samples collected from the wells were analyzed in accordance with EPA Methods 5030/8015m for total petroleum hydrocarbons quantified as gasoline (TPH-g), as diesel (TPH-d) and fuel additives ethanol and methanol, EPA method 602 for benzene, toluene, ethylbenzene and total xylenes (BTE&X), EPA method 8260 for volatile organic compounds, and in accordance with EPA Method 8260 modified for oxygenated fuel additives Two water samples from wells MW-4 and vapor well VW-I mere analyzed for dissolved iron and manganese in accordance with EPA method 6010 Two Nater samples were placed in a chilled container, under ice, and were transported under chain- of-custody hain- ofcustody to an independent microbiologist A Keith Kaufman for bio-enumeration and physicochemical analysis 30 FINDINGS ' 3 1 GROUND WATER ELEVATION AND GRADIENT ' The casing elevation of each v�ell was surveyed relative to a City of Stockton bench mark of known elevation The elevation of ground water in each well was calculated by subtracting the ground water ' depth from the sur\,eyed casing elevation The depth of ground water, casing elevations and ground elevations are tabulated in Table 1 The hydraulic gradient was inferred by contouring the elevation of ground water in each properly screened well Ground water gradient and flow direction calculations were also prepared from data collected from monitoring wells MW-1, MW-2 and MW-3 The tops of the screened intervals in these wells are 10 ' to 14 feet below the top of the saturated zone and the ground water elevations calculated from these wells may not be representative of the upper most water table hydrology This ground water gradient ,Aas calculated to be approximately 0 0055 ft/ft directed approximately N 27° E The ground water ' elevation contours for these three wells on the site are illustrated in Figure 3 - Ground Water Elevation Adtianced GeGEn%ironmental Inc